With the advent of a deep reactive ion etching (DRIE) process for forming slots and trenches in a substrate material, greater precision and control over the etching of substrates in higher speed processes has been obtained. DRIE is a dry etching process carried out under high vacuum by means of a chemically reactive plasma, wherein the constituents of the plasma are selected in congruence with the substrate to be acted upon. Before the adoption of DRIE techniques to form trenches or slots in semiconductor substrates, most trenches or slots in substrates having a thickness greater than about 200 microns thick were formed by mechanical blasting techniques or chemical *vet etching techniques. However, such mechanical techniques or chemical wet etching techniques are not suitable for newer products which demand higher tolerances and smaller fluid flow trenches or fluid supply slots. DRIE enables deep anisotropic etching of trenches and slots with greater tolerances and without regard to crystal orientation.
DRIE techniques have progressed incrementally towards a goal of etching high aspect ratio features in semiconductor substrates wherein the aspect ratio is on the order of 1:100 width to depth. Hence, much progress has been made in forming conduits or trenches with substantially perpendicular walls or walls having reentrant wall profiles. The process scheme for achieving high aspect ratio slots or trenches in semiconductor substrates includes a series of sequential steps of alternating etching and passivation. Such aniosotropic etching techniques are described in U.S. Pat. Nos. 5,611,888 and 5,626,716 to Bosch et al. the disclosures of which are incorporated herein by reference.
Accordingly, DRIE is a particularly suitable method of forming a fluid supply slot in a micro-fluid ejection head substrate. DRIE is a very desirable method because it has very good shelf control, does not induce chip cracking, and creates a very controllable wall angle profiles.
However, micro-fluid ejection heads made using the DRIE process have experienced an increase in ejected fluid misdirection and/or a decrease in droplet placement accuracy as the size of nozzle holes and flow features in the ejection heads continues to decrease. Such problems were not as evident in ejection heads having relatively larger nozzles and flow features. Accordingly, a need exists for a method of improving droplet placement accuracy for micro-fluid ejection heads. Since micro-fluid ejection heads may often be used as ink-jet print heads, the improvement of droplet placement accuracy may result in a desirable improvement in print quality.
With regard to the foregoing, there is provided a method for treating a substrate after a deep reactive ion etching (DRIE) process used to form fluid supply slots in a micro-fluid ejection head substrate. The method includes removing a residue from the substrate after the DRIE process. The method may include contacting the substrate with an aqueous tetramethyl ammonium hydroxide solution (TMAH). The method may also include stripping a photoresist etching mask from the substrate. The method may further include dissolving a passivating coating from the substrate. As a further step, the substrate may be contacted with an acidic solution then rinsing and drying the substrate.
Another embodiment of the present disclosure may provide a method of removing an AlFx residue from a substrate after a deep reactive ion etching (DRIE) process. The method may include contacting the micro-fluid ejection head with an aqueous solution of tetramethyl ammonium hydroxide (TMAH). The method may further include stripping a photoresist etch mask from the micro-fluid ejection head. The method may also include dissolving a passivating coating from the substrate. The substrate may then be contacted with an acidic solution before rinsing and drying the substrate.
In another embodiment there is provided a micro-fluid ejection head substantially devoid of AlFx, and made by the aforementioned process.
An advantage of the exemplary process disclosed herein may provide a method of removing an AlFx residue from a micro-fluid ejection head without adversely affecting the performance of the micro-fluid ejection head. As described in more detail below, it was found that the AlFx residue was formed during the DRIE process used to etch fluid supply slots through the substrate. It was also discovered that the AlFx residue, if not thoroughly removed after the DRIE process, may migrate to fluid flow portions of the ejection head. If the residue accumulates in the fluid ejection chamber or nozzles of the ejection head, misdirection of fluid ejection may occur upon ejection of the fluid. Accordingly, it has been found that droplet placement accuracy may be improved by the removal of the residue on the substrate after the DRIE process, which residue was found to comprise AlFx species.
It is contemplated, and will be apparent to those skilled in the art from the preceding description and the accompanying drawings, that modifications and changes may be made in the embodiments of the disclosure. Accordingly, it is expressly intended that the foregoing description and the accompanying drawings are illustrative of exemplary embodiments only, not limiting thereto, and that the true spirit and scope of the present disclosure be determined by reference to the appended claims.